…This successful taurine treatment led to the fortification of commercial cat foods, which already contained taurine, with additional taurine. Although this has resulted in the virtual disappearance of this condition, no systematic studies have been reported on the long term effects of a high taurine diet. The results of such a study are reported here.
Female cats were fed completely defined purified diets containing 0.05%, 0.2%, or 1% taurine for at least 6 months prior to breeding as described in detail elsewhere (1992). Breeding performance was evaluated and taurine concentrations in tissues and fluids of adults and offspring measured.
The high taurine diet had no effect on appetite, food consumption, weight gain, or estrus cycle of the adult females. The reproductive performance, if anything, was slightly better in the females fed the high taurine diet; the proportion of pregnancies reaching term, and the number of kittens surviving to weaning per term pregnancy was slightly greater for the cats fed 1% taurine than those fed 0.05% or 0.2% taurine although none of these trends was statistically-significant (Table 1). The growth rates of the kittens from females fed the different amounts of taurine were not statistically-significantly different although the greatest was achieved by the kittens from females fed the 0.05% taurine diet (Figure 1). This observation is supported by examination of the birth weights and 8-week-old weights of all kittens in this study (Table 2). The kittens at birth weigh more from females fed the greatest amount of taurine, whereas the reverse is true at 8 weeks of age. The brain weights of kittens from mothers fed 1% taurine were statistically-significantly greater than those of the other diet groups, both at birth and at 8 weeks of age. The concentration of taurine in the milk of the lactating females was greater in those fed the highest amounts of dietary taurine and generally increased during lactation (Figure 2).
Tissue taurine concentrations in adult cats fed the high taurine diet over an extended period of time (average 2.5 years) were greater in soft tissues and some muscles than controls, but not in retina or brain. Despite spending the entire gestation period in a taurine-enriched environment, newborn kittens from mothers fed 1% taurine had few tissues with statistically-significantly higher taurine concentrations. By weaning at 8 weeks after birth, such kittens had many tissues with greater taurine concentrations, including most brain regions. By 12 and 20 weeks after birth, most tissues had statistically-significantly greater taurine concentrations. Some representative values for tissues at different ages are provided in Table 3:
Taken together, these results indicate that the fully mature cat brain is largely resistant to statistically-significant increases in taurine concentration by consuming a high taurine
…The consequences of these differences, if any, are not obvious, and at this stage our studies provide no evidence of ill effects produced by prolonged feeding of high taurine diets to adult cats or on their offspring.
[This study seems like evidence that 1% taurine is not enough. There’s no evidence of ‘overshoot’ of an optimally-high dose, and all of the datapoints keep consistently indicating that the highest dose was best, despite often being quite crude or highly-indirect, like kitten weight.]